The term “phytosterols” as used herein covers both plant sterols, plant stanols, wood sterols, and wood stanols. Plant sterols are naturally occurring substances that are components of edible vegetable oils. Plant stanols, occurring in nature at a lower level, are saturated fatty acid compounds of the respective plant sterols. Wood sterols and wood stanols are also naturally occurring substances that are present in whole or in part from tall oil, a product derived during the processing of paper from wood. Commercial quantities of plant stanols are derived from the process of catalytic hydrogenation.
The use of phytosterols and phytosterol esters as cholesterol lowering adjuncts in a variety of food products has been well documented. As reported by the Institute of Food Science and Technology, sterols dissolved in edible fat products have been found to be more effective at reducing blood cholesterol levels than sterols in crystalline form. It is difficult to incorporate free sterols into edible fats or oils because of their insolubility, whereas sterols esterified to fatty acids are more fat soluble. The enrichment of foods such as margarines with phytosterols is one of the recent developments in functional foods to enhance the cholesterol-lowering ability of traditional food products.
While phytosterols possess desirable qualities in terms of potential for lowering cholesterol, they can pose challenges in the manufacture of food products for consumer use. While conventional fatty acids tend to form round crystal structures that promote spreadability and ease of handling, phytosterols tend to form sharp needle-like crystals at ambient temperatures that result in a brittle product. Such a product can be difficult for a manufacturer to work with, and can be less desirable to a consumer when used in products such as spreads
Typically, phytosterol esters are created by esterifying a phytosterol material with relatively high levels of mono- and polyunsaturated fatty acids, and with the fatty acids of long-chain triglycerides. Such products will be very viscous at 40° F., but can range from viscous to liquid at ambient temperature. These products are well suited for use in dressings and similar products, but may not be suitable for use in those applications in which the ingredient should be substantially solid at ambient temperature, such as margarine-type products and bakery shortenings, where hardness at room temperature can make them undesirable.
U.S. Pat. No. 6,106,886 discloses a process for the preparation of stanol fatty acid esters having any desired tatty acid groups, the preparation comprising the interesterification of stanol fatty acid esters with a source for one or more fatty acid moieties of a desired composition. Such sources for fatty acid moieties preferably contain high amounts of polyunsaturated fatty acid moieties.
U.S. Pat. No. 6,117,475 discloses fat based food products having an optimal ratio of free and esterified sterols, such products not showing instability and/or crystal formation.
U.S. Pat. No. 6,531,463 discloses a method of making a homogeneous and stable paste by mixing β-sitosterol and a food grade oil, heating until all the solids are dissolved in the oil, cooling the mixture, and adding water to disperse it.
U.S. Pat. No. 6,753,032 discloses a “plant sterol-containing fat composition . . . comprising a plant sterol fatty acid ester (A); and from 10 to 70% by weight of a partial glyceride (B).” The composition can be made by “effecting the esterification reaction of a plant sterol, and a partial glyceride and/or triglyceride under solventless conditions by using a lipase or an alkali as a catalyst.” (Col. 2, lines 32-42)
U.S. Pat. No. 6,800,317 discloses sterol and/or stanol fatty acid ester compositions, in which more than 50% of the fatty acid moieties comprises polyunsaturated fatty acids, and less than 7% comprises saturated fatty acids, and the composition shows no texturizing properties.
US 2004/0219277 discloses a fat blend including a reduced level of a conventional hardstock rich in absorbable saturated or a trans-unsaturated fat, wherein the solid fat component is composed of either fully a phytosterol ester or ester blend, defined as a texturizing agent, or of a blend of the texturizing agent and conventional hardstock.
US 2005/0038270 discloses a process for preparing sterol and stanol esters using a base-catalyzed transesterification of the free sterols with fatty acid glycerides coupled to removal of the produced glycerol under vacuum.
WO 98/06405 discloses a stanol composition containing sitostanol and a substantial amount of at least 10% campestanol; the composition can be esterified to provide a substance that can be used in fat-containing foods.
WO 01/91587 A2 discloses an oil composition comprising triglycerides bearing short and medium chain fatty acid residues derived from fatty acids having from 4 to 14 carbon atoms and long chain fatty acid residues derived from fatty acids having from 15 to 22 carbon atoms.
Bailey's Industrial Oils and Fat Products, vol. 2, 4th ed., edited by Daniel Swern, at pp. 113-124 discloses the background of esterification and a general process for carrying out esterification reactions.
It is thus an object of the invention to provide a phytosterol based product that is substantially solid at room temperature, so as to be suitable for use in margarine and/or bakery shortenings.
It is another object of the invention to provide a phytosterol-based product that is substantially solid at room temperature, and that provides greater cholesterol-lowering potential than standard saturated fats that are solid at room temperature.
It is still another object of the invention to provide a phytosterol based product that is substantially solid at room temperature, and yet is spreadable at room temperature, so as to be useful in spreads and other food products desirable to consumers.
It is another object of the invention to provide a method for making such a phytosterol product.